Use of corrugated paperboard for skin packaging substrates

ABSTRACT

Corrugated paperboard substrate is moved through a skin packaging machine with its corrugations oriented transversely to direction of advance. Lengthwise extending marginal edge portions of the substrate are maintained compressed, at least all along that portion of the substrate that is over the suction nozzle, thereby preventing air from leaking into the corrugations.

United States Patent Walus 1 Sept. 3, 1974 USE OF CORRUGATED PAPERBOARDFOR SKIN PACKAGING SUBSTRATES Richard L. Walus, Minneapolis, Minn.

Assignee: Possis Corporation, Minneapolis,

Minn.

Filed: July 23, 1973 Appl. No.: 382,075

Inventor:

U.S. Cl 53/22 A, 53/112 A, 53/140 Int. Cl 1365b 33/02 Field of Search53/22 A, 112 A, 140

References Cited UNITED STATES PATENTS Goodman 53/22 A 3,468,099 9/1969Vogt 53/140 Primary Examiner-Travis S. McGehee Attorney, Agent, orFirm-Ira Milton Jones [5 7 1 ABSTRACT Corrugated paperboard substrate ismoved through a skin packaging machine with its corrugations orientedtransversely to direction of advance. Lengthwise extending marginal edgeportions of the substrate are maintained compressed, at least all alongthat portion of the substrate that is over the suction nozzle, therebypreventing air from leaking into the corrugations.

6 Claims, 4 Drawing Figures or-mole 5 PATENTED I974 V 3.832.821

SNEEI 30? 3,

USE OF CORRUGATED PAPERBOARD FOR SKIN PAQKAQLNQ SUBSTRATES Thisinvention relates to so-called skin packaging in which an articlemounted on a substrate of paperboard or the like is protected andsecured to the substrate by a film of thermoplastic material that coversthe article and its adjacent face portions of the substrate; and theinvention is more particularly concerned with a method and means forenabling corrugated paperboard to be used as a skin packaging substrate.

Two general types of skin packaging are practiced. In one, athermoplastic sheet that has been heated to soften it is draped over asubstrate and an article or articles thereon. In the other, fluidthermoplastic material is debouched downwardly from a nozzle or die toform a film that covers the substrate and articles.

In both cases satisfactory skin packaging requires that the spacebetween the substrate and the film be substantially completely evacuatedof air before the thermoplastic cools to hardness, to insure that thefilm will not have wrinkles, blisters or bubbles. To this end thesubstrate is moved through the skin packaging machine directly from thestation at which film is applied to a vacuum table or a suction nozzleby which suction is applied to its underside. The substrate is either aninherently porous material or one that has been provided with numerousvery small perforations, to permit air to be drawn downwardly through itfrom beneath the film.

Obviously the complete evacuation of the space heneath the film requiresthat air should not be permitted to enter the vacuum chamber or suctionnozzle except from that space. Because of this requirement, it hasheretofore been considered impracticable to use corru-- gated paperboardas a substrate for skin packaging.

Such material, as is well known, comprises two laminations of paper thatare held in flatwise spacedapart relationship by an intervening layer ofcorrugated paper. If suction is applied to the undersurface of the lowerlamination, no air would normally be drawn through the upper one becauseof the leakage along the corrugations, which, in effect, define a seriesof open tubes along which air can flow freely.

In all other respects, however, corrugated paperboard is an idealmaterial for skin packaging substrate. It is strong, rigid, light inweight, andaffords a degree of cushioning and impact protection that isoften of value for the packaging of fragile articles.

With these considerations in mind, it is the general object of thepresent invention to provide a method and means for enabling corrugatedpaperboard to be use as a skin packaging substrate.

More specifically it is an object of this invention to provide a simplemethod of sealing the ends of the open tubes that are defined by thecorrugations of corrugated paperboard, so that when suction is appliedto one surface of the paperboard air is prevented from leaking intothose tubes and is instead constrined to flow transversely through thepaperboard from its other surface.

It is also a specific object of this invention to provide inexpensiveapparatus for the practice of that method that can be readily installedon conventional skin packaging machines.

With these observations and objectives in mind, the manner in which theinvention achieves its purpose will be appreciated from the followingdescription and the accompanying drawings, which exemplify theinvention, it being understood that changes may be made in the precisemethod of practicing the invention and in the specific apparatusdisclosed herein without departing from the essentials of the inventionset forth in the appended claims.

The accompanying drawings illustrate one complete example of anembodiment of the invention constructed according to the best mode sofar devised for the practical application of the principles thereof, andin which:

FIG. 1 is a more or less diagrammatic perspective view of a portion of askin packaging machine that embodies the principles of the presentinvention;

FIG. 2 is a view in side elevation of the portion of the machine shownin FIG. 1, FIG. 2 also being somewhat diagrammatic;

FIG. 3 is a view in cross section, taken on the plane of the line 3-3 inFIG. 2; and

FIG. 4 is a view in longitudinal section, on an enlarged scale, taken onthe plane of the line 4-4 in FIG. 3.

Referring now more particularly to the accompanying drawings, thenumeral 5 designates generally a skin packaging machine of the typedisclosed in US. Pat. No. 3,596,432, to MJ. Straub et a], to whichreference may be made for a more detailed description of such a machine.As is conventional, the machine 5 comprises means 6 for moving asubstrate 7 in one direction along a horizontal path. In this case thesubstrate is carried along on a conveyor which comprises a flat belt 8trained around rollers 9 that are spaced apart in the direction ofconveyor travel.

The substrate 7 is conventional corrugated paperboard which, as bestseen in FIG. 4, comprises two laminations 10 and 11 of kraft paper heldin flatwise spaced apart relationship by an intervening layer ofcorrugated paper 12.

In the present case the substrate is in the form of a continuous stripor web, drawn from a roll or other supply source .which is not shown butwhich will be understood to be located to the right of the portion ofthe machine depicted in FIGS. 1 and 2. To the left of the illustratedportion of the machine there can be a flying guillotine (not shown), asdescribed in the above mentioned patent, for cutting the substrate intoindividual packaging lengths. Of course the machine 5 can be used withsubstrate that has been precut into panels.

Irrespective of whether the substrate is a continuous strip or indiscrete lengths, it has its corrugations oriented transversely to thelength of the conveyor for the purposes of this invention.

In the present case articles 13 to be packaged are illustrated asbar-like items, and it will be understood that these have been placed onthe substrate, at regular intervals along its length, by means of knownapparatus not illustrated.

Although the present invention is entirely suitable for skin packagingmethods and apparatus wherein a heat softened sheet of thermoplasticmaterial is draped over an article and a substrate, the machine hereillustrated is of the type that comprises a die or nozzle 15 which ismounted above the conveyor. As the conveyor advances at a steady rate,liquid plastic issues downwardly from the nozzle 15 in a curtain-likestream and forms a continuous coating or film 26 over the articles andthe substrate.

Immediately after passing beneath the nozzle 15, the substrate iscarried over a suction nozzle 16 that applies suction to its undersideto evacuate the space between the substrate and the plastic film. Asshown, the suction nozzle extends a substantial distance lengthwisealong the conveyor and nearly completely across it, being in the form ofa shallow pan that opens to the underside of the top stretch of theconveyor belt 8. Numerous holes 17 through the belt 8, at intervals allalong its length and across most of that part of its width that isoverlain by the substrate, allow air to be drawn through it from thesubstrate into the suction nozzle. The top stretch of the belt 8 rideson a coplanar rim or top edge 18 of the suction nozzle to form a slidingseal around its mouth as well as to be locally supported by it.

it will be understood that the laminations 10 and 11 of the substrate,and also the corrugated layer 12 thereof, are either porous or areprovided with numerous tiny perforations, so that air can readily passthrough the substrate from one of its surfaces to the other.

To prevent leakage of air into the space between the laminations l0 and11 of the substrate, the present invention contemplates that thelengthwise extending marginal edge portions 19 of the substrate shall bemaintained under firm compression all along at least that portion of thesubstrate that overlies the suction nozzle 16. Such compression ofcourse seals the ends of the tubes that are defined by the corrugations.

The means for effecting such sealing compression comprises two sets ofrollers 20, one set over each side edge portion of the conveyor. Theaxes of. the rollers extend horizontally and traversely to the directionof conveyor travel, and all of the rollers in each set are radiallyaligned with one another to have a belt 22 trained around them. The belt22 serves to distribute the compressive force due to the rollers fairlyevenly along that portion of the substrate margin that the rollersoverlie.

The rollers 20 are of course freely rotatable so that they and the belt22 are driven by the conveyor belt 8 through the substrate. Preferably,as indicated in FIG. 2, the rollers 20 are so mounted as to be capableof limited bodily up and down motion independently of one another, andeach is urged downwardly with a fairly strong biasing force. Suchmounting of the rollers enables them to accommodate themselvesautomatically to corrugated paperboard substrates of different weightsand also to variations in thickness along the length of a particularsubstrate.

Obviously the plastic film material should not be applied to themarginal zones 19 of the substrate that are engaged by the compressingbelts 22, since the plastic is still in a fluid or tacky state as thesubstrate moves across the suction nozzle 16 and would stick to thosebelts. Preferably the compressed and uncoated marginal edge portions ofthe substrate are cut off and discarded after the substrate has passedthe suction nozzle.

The corrugated layer of the substrate is of course relatively resistantto compression, but once broken down it can be rather easilyrecompressed and maintained in compressed condition. Preferably theroller sets 20 and their cooperating belts 22 merely maintaincompression of the marginal portions of the substrate, and the initialbreaking down of the corrugated layer is effected by a pair of singlerollers 24, one mounted at each side of the conveyor, at a zone upstreamfrom the suction nozzle. As shown, the rollers 24 are located to engagethe substrate just before it is carried under the die from which thethermoplastic film material issues. Like the roller sets 20, the singlerollers 24 are freely rotatable, are mounted for bodily up and downmotion, and are yieldingly biased downwardly. inasmuch as they engageonly small areas of the substrate, they can exert high compressiveforces upon it to flatten the corrugated layer.

From the foregoing description taken with the accompanying drawings itwill be apparent that this invention provides a simple method andinexpensive means for enabling the use of corrugated paperboardsubstrates for skin packaging.

Those skilled in the art will appreciate that the invention can beembodied in forms other than as herein disclosed for purposes ofillustration.

I claim 1. In the packaging process in which articles to be packaged areplaced upon substrate and the substrate is moved-horizontally in onedirection along a defined path, a thermoplastic film is applied over thearticles and the substrate, and suction is thereafter applied to theunderside of the substrate in one zone of said path to draw air throughthe substrate and thus suck the film down into intimate engagement withit and the articles thereon, the improvement which enables use forsubstrate of corrugated paperboard comprising two paper laminations heldin flatwise spaced relation by an intervening layer of paper havingparallel corrugations which allow air to flow edgewise between thelaminations, said improvement residing in the steps of:

A. orienting the substrate with the corrugations extending transverselyto said direction; and

B. maintaining 'sufficient compressive force upon each of the marginaledge portions of the substrate that extends in said direction, all alongat least that portion of the same that extends through said zone, toseal the paper laminations to one another and thus prevent edgewise flowof air between them.

2. The process of claim 1, further characterized by:

C. prior to entry of the substrate into said zone, ap-

plying a localized compressing force to each of said marginal edgeportions of the substrate as the substrate moves in said direction, tobreak down the corrugations of said intervening layer at said marginaledge portions thereof and thus facilitate maintenance of sealingcompression at said zone.

3. A packaging machine comprising means for effecting lengthwise motionalong a defined path of an elongated horizontal substrate carryingarticles at spaced intervals therealong, means for applying athermoplastic film over the substrate and the articles, and means at azone along said path for drawing air through the substrate and thussucking film down into intimate engagement with the substrate and thearticles thereon, said machine being characterized by means that enableit to operate successfully with corrugated paperboard substrate thatcomprises two paper laminations held in flatwise spaced relation by anintervening layer of paper having parallel corrugations which extendtransversely to said path and which allow air to flow edgewise betweenthe laminations, the last mentioned means comprising:

means positioned to engage and collapse the longitudinal marginal edgeportions of the substrate as it approaches said zone, and thereby sealthe ends of the transversely extending corrugations.

4. A packaging machine comprising means for effecting lengthwise motionalong a defined path of an elongated horizontal substrate carryingarticles at spaced intervals therealong, means for applying athermoplastic film over the substrate and the articles, and means at azone along said path for drawing air through the substrate and thussucking film down into intimate engagement with the substrate and thearticles thereon, said machine being characterized by means that enableit to operate successfully with corrugated paperboard substrate thatcomprises two paper laminations held in flatwise spaced relation by anintervening layer of paper having parallel corrugations which extendtransversely to said path and which allow air to flow edgewise betweenthe laminations, the last mentioned means comprising:

means extending lengthwise along each longitudinal marginal edge portionof the substrate through at ginal edge portions of the substrate asitmoves through said zone;

B. two sets of rollers at said zone, one set at each side of said path,

1. all of said rollers being rotatable on axes that extend transverselyto said path,

2. the rollers of each set being radially aligned with one another andspaced in said direction at intervals along said zone, and

3. each of said rollers being mounted for limited independent bodily upand down motion and being yieldingly urged downwardly; and

C. a belt trained around each set of rollers and through which thecompressive force of the rollers of the set is imposed upon anddistributed along a marginal edge portion of the substrate.

6. The packaging machine of claim 5, wherein all of said rollers aremounted for free rotation, further characterized by:

D. an additional pair of freely rotatable rollers, one at each side ofsaid path, at a location in advance of said zone relative to thedirection of substrate motion, each of the rollers of said additionalpair being freely rotatable on a horizontal axis transverse to said pathand being mounted for limited bodily up and down motion and biaseddownwardly with sufficient force to break down the corrugations of saidintervening layer of the substrate along said marginal edge portionsthereof.

1. In the packaging process in which articles to be packaged are placedupon substrate and the substrate is moved horizontaLly in one directionalong a defined path, a thermoplastic film is applied over the articlesand the substrate, and suction is thereafter applied to the underside ofthe substrate in one zone of said path to draw air through the substrateand thus suck the film down into intimate engagement with it and thearticles thereon, the improvement which enables use for substrate ofcorrugated paperboard comprising two paper laminations held in flatwisespaced relation by an intervening layer of paper having parallelcorrugations which allow air to flow edgewise between the laminations,said improvement residing in the steps of: A. orienting the substratewith the corrugations extending transversely to said direction; and B.maintaining sufficient compressive force upon each of the marginal edgeportions of the substrate that extends in said direction, all along atleast that portion of the same that extends through said zone, to sealthe paper laminations to one another and thus prevent edgewise flow ofair between them.
 2. The process of claim 1, further characterized by:C. prior to entry of the substrate into said zone, applying a localizedcompressing force to each of said marginal edge portions of thesubstrate as the substrate moves in said direction, to break down thecorrugations of said intervening layer at said marginal edge portionsthereof and thus facilitate maintenance of sealing compression at saidzone.
 2. the rollers of each set being rAdially aligned with one anotherand spaced in said direction at intervals along said zone, and
 3. eachof said rollers being mounted for limited independent bodily up and downmotion and being yieldingly urged downwardly; and C. a belt trainedaround each set of rollers and through which the compressive force ofthe rollers of the set is imposed upon and distributed along a marginaledge portion of the substrate.
 3. A packaging machine comprising meansfor effecting lengthwise motion along a defined path of an elongatedhorizontal substrate carrying articles at spaced intervals therealong,means for applying a thermoplastic film over the substrate and thearticles, and means at a zone along said path for drawing air throughthe substrate and thus sucking film down into intimate engagement withthe substrate and the articles thereon, said machine being characterizedby means that enable it to operate successfully with corrugatedpaperboard substrate that comprises two paper laminations held inflatwise spaced relation by an intervening layer of paper havingparallel corrugations which extend transversely to said path and whichallow air to flow edgewise between the laminations, the last mentionedmeans comprising: means positioned to engage and collapse thelongitudinal marginal edge portions of the substrate as it approachessaid zone, and thereby seal the ends of the transversely extendingcorrugations.
 4. A packaging machine comprising means for effectinglengthwise motion along a defined path of an elongated horizontalsubstrate carrying articles at spaced intervals therealong, means forapplying a thermoplastic film over the substrate and the articles, andmeans at a zone along said path for drawing air through the substrateand thus sucking film down into intimate engagement with the substrateand the articles thereon, said machine being characterized by means thatenable it to operate successfully with corrugated paperboard substratethat comprises two paper laminations held in flatwise spaced relation byan intervening layer of paper having parallel corrugations which extendtransversely to said path and which allow air to flow edgewise betweenthe laminations, the last mentioned means comprising: means extendinglengthwise along each longitudinal marginal edge portion of thesubstrate through at least said zone for imposing sufficient compressiveforce upon said marginal edge portions to maintain a seal between thetwo laminations thereof.
 5. The packaging machine of claim 4, whereinsaid means for imposing compressive force upon the marginal edgeportions of the substrate comprises: A. means for supporting at leastthe longitudinal marginal edge portions of the substrate as it movesthrough said zone; B. two sets of rollers at said zone, one set at eachside of said path,
 6. The packaging machine of claim 5, wherein all ofsaid rollers are mounted for free rotation, further characterized by: D.an additional pair of freely rotatable rollers, one at each side of saidpath, at a location in advance of said zone relative to the direction ofsubstrate motion, each of the rollers of said additional pair beingfreely rotatable on a horizontal axis transverse to said path and beingmounted for limited bodily up and down motion and biased downwardly withsufficient force to break down the corrugations of said interveninglayer of the substrate along said marginal edge portions thereof.